A
mother announced one Christmas that she was no longer going to remind her
children to write their thank-you notes. As a result their grandmother never
received acknowledgement of the generous cheques she had given her grandchildren.
The next year, however, things were different. "The children came over in
person to thank me," the grandmother told a friend triumphantly. "How
wonderful!" the friend exclaimed. "What do you think caused the change
in behaviour?" "Oh, that's easy," the grandmother replied. "this
year I didn't sign the cheques."